“To utilize these structures in biomimetic technology, engineers require a detailed understanding of their behavior and makeup,” commented the lead author of the study, Skoltech Photonics PhD student Julijana Cvjetinovic. “This particular study furnishes unprecedented new insights into how the static and dynamic mechanical properties of diatom frustules are related to their structure.”
Diatoms attracted the attention of scientists soon after the invention of the optical microscope in the 17th century. Although our understanding of these algae is still incomplete, our microscopy tools have also become better and more versatile. University of Oxford’s Alexander Korsunsky, the co-principal investigator of the study and a visiting professor at Skoltech, said: “After a quarter of a century of my working on the topic, it is satisfying for me to see the good use of nanoindentation inside the Tescan Solaris focused ion beam scanning electron microscope, acquired by Skoltech upon my recommendation and now housed at the Institute’s Advanced Imaging Core Facility. Eugene Statnik’s and Pavel Somov’s virtuoso use of this complex setup made it possible to collect unique video evidence of diatom deformation, whilst Sergey Luchkin’s masterful application of atomic force microscopy enabled the quantitative evaluation of the elastic modulus and hardness.”
By combining atomic force microscopy and nanoindentation — that is, poking the sample with a diamond tip and measuring its deflection — the team explored the mechanical properties of both dried frustules and wet ones with the organic material intact. The analysis encompassed hardness, flexibility, and vibrational characteristics, investigating how they are related to the frustules’ complex structure with two layers and distinct patterns of pores on the inside and on the outside. The interrogated algae ranged from 30 to 40 micrometers in diameter.
“Perhaps the most exciting feature we have identified is this distinction between the harder inner layer that serves as a foundation, and the softer and more porous outer layer on top of it. It was exciting to see the frustules oscillate but not break under cyclic loading, confirming our surmise about the origins of their flexibility and strength. We are the first to observe this behavior and to report the comparative mechanical characteristics of living diatom cells and cleaned frustules without the organic components,” Cvjetinovic added.
The co-principal investigator of the study, Professor Dmitry Gorin, who heads Skoltech’s Biophotonics Lab, said: “We believe that further inquiries into diatom frustules will eventually provide a pathway to the diverse range of currently anticipated applications — from MEMS microphone membranes that visibly resemble algae [see image below] to composite materials that replicate the diatom structure and incorporate additional components and functions.”
The study is an example of collaboration of researchers from three Skoltech centers: Photonics, Energy, and Engineering.
The research reported in this story was supported by the Russian Science Foundation (Grant No. 22-14-00209, project manager: Professor Dmitry Gorin) and the Russian Ministry of Science and Higher Education (Project No. 121032300019-0).